1. Technical Field
The present invention relates to methods of localizing lesions. More specifically, the present invention relates to methods of localizing lesions using radioactive seeds.
2. Background Art
Localization of non-palpable lesions for biopsy or excision during surgery is a necessary procedure. Several techniques are currently available. As described herein, these techniques have several disadvantages and improved methods are needed.
Mammography is credited with the detection of clinically occult cancer of the breast at greater than 80% sensitivity. Since breast biopsies increase the overall cost of screening for breast cancer and 70% of the detected lesions are benign, there is controversy regarding the cost effectiveness of such biopsies. Therefore, the development of more effective biopsy techniques are a significant goal.
There are three different ways to biopsy occult breast lesions. These include xe2x80x9ccore-needlexe2x80x9d biopsy, xe2x80x9cABBIxe2x80x9d (Advanced Breast Biopsy Instrumentation), and open surgical excision biopsy. Open surgical excision biopsy, using needle localization, has been the standard for diagnosis of non-palpable lesions in the breast for the past 20 years.
Although needle localized breast biopsy (NLBB) has some advantages, it has several disadvantages. It requires highest-level skill in placement by radiologists. The method requires flexible wires which are difficult for surgeons to palpate. Currently used wires may be dislodged during transfer of the patient, or displaced from the site of the radiographically located suspicious lesion. When cut inadvertently with scissors, the wires may leave metal fragments in the patient""s breast, which has resulted in litigation. A potential for thermal injury to the breast exists when electrocautery is used near the wire. If the insertion site of the wire is too far from the lesion, there is a dilemma in planning the incision to include both the wire and the lesion. This situation can lead to removing more breast tissue than necessary. There are increased costs related to additional x-rays which are used to confirm that the lesion has been excised, longer operating room time fees, specimens require transfer to radiology by operating room personnel, taking a film of the specimen by a radiology technician and finally interpretation and notification by a radiologist.
Recently, several patents have issued pertaining to devices and methods for the removal of lesions from soft tissue. However, these patients do little to overcome the problems detailed above. Specifically, U.S. Pat. No. 5,807,276 to Russin, issued September 1998, discloses a device and method for using a K-wire which is positioned through the lesion to be removed. This device requires that selectable wires be used which can be difficult to maneuver and may cause infection if not properly sterilized.
U.S. Pat. No. 5,833,627 to Shmulewitz et al., issued November 1998, also discloses a needle or cannula of a biopsy device for insertion into the tissue. This is accomplished by correlating, in real-time, the actual needle or cannula position with its probable trajectory once inserted. There is a large amount of speculation involved in the insertion of the needle into the breast or other soft tissue, thus increasing the possibility of removing more soft tissue than is necessary.
Finally, U.S. Pat. No. 5,855,554 to Schneider et al., issued January 1999, discloses support plates which contain the breast. The plates include grids with reference markers for localization and windows for allowing the physician access to the breast. A thick biopsy plate containing a plurality of holes fits into the grid opening through which the biopsy needle is inserted. Again, the same problems pertaining to the insertion of wires or needles can occur which can lead to the removal of excess breast tissue.
Although the above discussed biopsies are done for the diagnosis of cancer, it is imperative that physicians treat the lesions as if they are malignant until it is histologically proven otherwise. Lesions should be removed by the most direct approach, as opposed to tracking the lesion and needle through breast tissue. The surgeon also needs to be aware of the placement of the incision so that if a mastectomy is necessary in the future, the biopsy scar can be cleanly excised.
It is therefore desirable to develop a method whereby mammographically detected lesions can be localized and excised in a safe, expeditious, and cost effective manner with the application of current technologies.
According to the present invention, there is provided a method of removing lesions by implanting a radioactive seed at the location of the lesion, locating the lesion for surgery by detecting the radioactivity of the implantedradioactive seed, and removing the lesion with the radioactive seed.
The present invention provides a method of removing lesions from soft tissues or bone by implanting a radioactive seed at the location of the lesion, locating the lesion by detecting radioactivity from the radioactive seed and then removing the lesion along with the radioactive seed.
The present method utilizes radiographic imaging or x-ray techniques such as CT scan, PET scan, MRI, or mammography to ensure that the radioactive seed is implanted in the exact location of the lesion, thus eliminating unnecessary removal of soft tissue, such as breast tissue, during the biopsy.
As further defined and explained below, the term xe2x80x9cimplantedxe2x80x9d means placing by needle placement, needle localization, surgery, injection or otherwise, the radioactive seed proximate to or within the lesion. This provides a precise target for the surgeon based upon a reliable identification of the lesion by radiographic imaging. By radioactive seed, it is meant that a radioactive, inert pellet is utilized. Such pellets can be made from an implantable metal, such as titanium, and the pellet also contains a radioisotope. The radioimmission can be gamma radiation or other emissions which are benign to the lesion and tissue and can just be detected by known detecting devices and methods. An example of such a radioactive seed is disclosed in U.S. Pat. No. 5,460,592 to Langton et al., assigned to Amersham.
In the past, radioactive seeds have been used for temporary as well as permanent implantation. The recaptured seeds can be sterilized for reuse. The most popular use for therapeutic seeds have been in the treatment of meningiomas and prostate cancer. At the Moffitt Cancer Center, improved seed placement technique has been developed for prostate brachytherapy, which has significantly contributed to the decreased morbidity and increased efficacy of the procedure.
The use of low dose seeds, which are temporarily placed, are useful for diagnostic purposes by guiding the biopsy of the suspicious lesion with the assistance of a hand-held gamma detecting probe (Navigator, USSC, Neoprobe, Dublin) or other radiation detecting device, such as a beta radiation detecting device. The present invention utilizes a single 125-I seed of the lowest possible activity ( less than 0.30 mci). This amount of radioactivity is significantly less than a standard mammogram or chest x-ray, however can be detected by the hand-held gamma probe to guide the surgeon in the biopsy process.
These probes have been especially designed to assist in detecting radioactive materials used for diagnostic purposes during surgery. Examples of these procedures include radioimmunoguided surgery (RIGS) for the detection of colorectal tumors and sentinel lymph node mapping for melanoma and breast cancer. Sentinel lymph node mapping, a procedure well known to the Moffit Cancer Center, involves injecting filtered technetium-99 labeled sulfur colloid (450 uci/5 cc) at the primary tumor site and allowing time for this substance to infuse the lymphatic channels. The seed guided breast biopsy utilize radioactive material which would be contained in titanium and have no direct contact with the tissue.
More specifically, the present invention provides a method of localization using the radioactive seeds and hand-held gamma detectors for surgery. The radioactive seed is localized to a lesion by use of imaging technology. The surgeon can then determine the location of the seed during surgery using a hand-held gamma detector. This allows localization without guide wires, a potential source of infection. Further it reduces the number and location of incisions that must be made and which must be considered in future surgeries.
The radioactive seed can be placed and localized to at least the bone, brain, lung, GI tract, intestines, stomach, liver, kidneys, GU tract including prostate, soft tissues, fatty lesions or muscle, pancreas, adrenal or any other site that can be radiographically images or otherwise localized.
Localization can be done with standard radiographs such as mammograms, ultrasound, MRI, CT scan or any other scanning technology that can localize an otherwise non-visible or non-palpable lesion.
In one example of the method, radioactive-guided breast biopsy is utilized. It is a safe, expeditious and cost-effective technique to biopsy non-palpable breast lesions. Low dose radioactive seeds are disposed proximate to a lesion under radiographic guidelines. The seeds are localize the non-palpable breast lesion which allows them to be more effectively excised with reduced operative time.
In a further example of the use of the present invention, interstitial brachytherapy is used. Interstitial brachytherapy has had many applications in the treatment of various malignant neoplasms. The development of accurate placement of radioactive seeds has eliminated many of the problems related to interstitial brachytherapy from past years. A variety of seeds have been developed to take advantage of their individual characteristics. The most widely used radioactive seed for prostate brachytherapy incorporates I-125, however any seed can be used which is detectable by a radiation sensing device. The iodine source is encapsulated in a titanium shell. The titanium combines low radiation absorption with good strength and tissue tolerance. I-125 has a half-life of 60 days and a gamma radiation of only 27 kev. The seeds are available at a length of 4.5 mm and diameter of 0.8 mm, which passes easily through a standard 18-gauge needle.
The above discussion provides a factual basis for the use of radio guided seed localization of imaged lesions. The utility of the present invention is shown by the following non-limiting examples.